Guidable intravascular blood pump and related methods

ABSTRACT

An improved intravascular blood pump and related methods involving the broad inventive concept of equipping the intravascular blood pump with guiding features such that the intravascular blood pump can be selectively positioned at a predetermined location within the circulatory system of a patient.

RELATED APPLICATIONS

This application is continuation of U.S. patent application Ser. No.12/772,810, filed May 3, 2010 (now U.S. Pat. No. 8,888,728), which is acontinuation of U.S. patent application Ser. No. 11/375,926, filed Mar.15, 2006 (now U.S. Pat. No. 7,731,675, issued Jun. 8, 2010), which is adivisional of U.S. patent application Ser. No. 10/070,178, filed Jul.19, 2005, (now U.S. Pat. No. 7,022,100, issued Apr. 4, 2006) which is aU.S. National Stage Entry of International Patent Application No.PCT/US00/24515 filed Sep. 1, 2000, which claims the benefit ofprovisional U.S. Patent Application Ser. No. 60/152,249 field Sep. 3,1999, all of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates generally to blood pumps and, moreparticularly, to an improved intra-vascular blood pump having a guidemechanism which provides the ability to selectively guide theintravascular pump to a desired location within a patient's circulatorysystem.

DESCRIPTION OF RELATED ART

Over the years, various types of blood pumps have been developed for thepurpose of augmenting or replacing the blood pumping action of damagedor diseased hearts. Blood pumps are commonly used in three situations:(1) for acute support during cardio-pulmonary operations; (2) forshort-term support while awaiting recovery of the heart from surgery; or(3) as a bridge to keep a patient alive while awaiting hearttransplantation. The pumps may be designed to provide right and/or leftventricular assist, although left ventricle assist is the most commonapplication in that it is far more common for the left ventricle tobecome diseased or damaged than it is for the right ventricle.

Blood pumps must provide leak-free operation and must avoidcontamination of the fluid by the pump components and the externalenvironment. Such pumps must also pump the fluid at a suitable ratewithout applying excessive Reynolds shear stress to the fluid. It iswell known to those skilled in the art that lysis or cell destructionmay result from application of shear stress to cell membranes. Red bloodcells are particularly susceptible to shear stress damage as their cellmembranes do not include a reinforcing cytoskeleton to maintain cellshape. Lysis of white blood cells and platelets also occurs uponapplication of high shear stress. Lysis of red blood cells can result inrelease of cell contents which trigger subsequent platelet aggregation.Sublytic shear stress leads to cellular alterations and directactivation and aggregation of platelets and white blood cells.

Intravascular blood pumps comprise miniaturized blood pumps capable ofbeing percutaneously or surgically introduced into the vascular systemof a patient, typically to provide left and/or right heart support. Onetype of intravascular pump is an axial flow blood pump comprising acable-mounted rotor surrounded by a protective shroud. The pump, alongwith the rotor and shroud, are mounted at the end of an elongatedflexible catheter. The catheter is inserted into the aorta from a remoteentry point, such as an incision below the groin that provides accessinto a femoral artery. The catheter then passes through the descendingaorta until it reaches the ascending aorta, near the heart. The catheterdevice encloses a rotating drive cable which is coupled to the impellerblade at one end, and which emerges from the exposed end of thecatheter, near the patient's groin, at the other end. When the exposedend of the drive cable is mechanically rotated, using a device locatedoutside the patient's body, it conveys the rotational force through thelength of the catheter, causing the impeller to spin at high speed nearthe heart. This type of blood pump finds particular application inproviding ventricular assist during surgery or providing temporarybridging support to help a patient survive a crisis.

While generally effective in providing ventricular assisting functions,prior art intravascular blood pumps nonetheless suffer variousdrawbacks. A significant drawback is that prior art intravascular bloodpumps are difficult to guide into the appropriate position within thecirculatory system of a patient. This is due largely to the fact thatthe elongated catheter is incapable of providing the degree of controlnecessary to easily negotiate the pump through the tortuous pathwaysleading up to and into the heart. When attempting to place the bloodpump in a trans-valvular configuration (with the inlet in the leftventricle and the pump outlet in the ascending aorta), the naturaltendency of the catheter to stay straight may cause the pump to beinadvertently placed in the carotid ostia, which can be dangerous if thepump is operated to withdraw blood from the brain.

To overcome these difficulties, certain guide mechanisms may be employedto assist the physician placing the pump in the appropriate positionwithin the circulatory system. One type of supplemental guide mechanismis a guide catheter. Guide catheters are designed with certainguidability characteristics such that physicians can selectivelyposition them within the vasculature or heart with relative ease. Acentral lumen is provided within the guide catheter such that theintravascular pump may be introduced therein and guided while it isadvanced towards the predetermined circulatory site. While generallyeffective at providing a guiding feature for such intravascular bloodpumps, employing such supplemental guide mechanisms is nonethelessdisadvantageous in that they consume valuable space within the vessels.A guide catheter, for example, would necessarily be larger in diameterthan the diameter of the pump and protective shroud in order to provideadequate passage of those components. As will be appreciated, thisrestricts the amount of space available for blood to flow within theparticular vessel, and increases the size of the required puncture woundfor accessing the vessel.

The present invention is directed at eliminating and/or reducing theeffects of the foregoing drawbacks of prior art intravascular bloodpumps.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art byproviding an improved intravascular blood pump equipped with integratedfeatures for selectively guiding the intravascular blood pump to apredetermined location in the patient's circulatory system, i.e. heartand/or vasculature. In so doing, the intravascular blood pump of thepresent invention eliminates the need for supplemental guidingmechanisms, such as a separate, large diameter guide catheter as used inthe prior art.

In a first broad aspect of the present invention, an intravascular bloodpump system is provided comprising an intravascular blood pump having acannula coupled thereto and an “over-the-wire” type guide mechanism forselectively positioning the intravascular blood pump and cannula at apredetermined location within the circulatory system of a patient. Toaccomplish this, a central lumen is formed through at least a portion ofthe intravascular blood pump system such that a guide element, such as aguide wire, may be progressed therethrough and advanced to thepredetermined location in the circulatory system of the patient. Afterthe guide element is advanced to this desired location, theintravascular blood pump and cannula may thereafter be advanced alongthe guide element to the desired location.

In a second broad aspect of the present invention, an intravascularblood pump system is provided comprising an intravascular blood pumphaving a cannula coupled thereto and a “side-rigger” or “rapid exchange”type guide mechanism for selectively positioning the intravascular bloodpump and cannula at a predetermined location within the circulatorysystem of a patient. To accomplish this, a side lumen is formed along alength of at least one of the intravascular blood pump and the cannula.A guide element, such as a guide wire, may be advanced to thepredetermined location in the circulatory system of the patient. Afterthe guide element is advanced to this desired location, theintravascular blood pump and cannula may thereafter be advanced alongthe guide element to the desired location.

In a third broad aspect of the present invention, an intravascular bloodpump system is provided comprising an intravascular blood pump having acannula coupled thereto and a “guide catheter” type guide mechanism forselectively positioning the intravascular blood pump and cannula at apredetermined location within the circulatory system of a patient. Thepump system of this broad aspect includes a conduit assembly and aseparate pump assembly. The conduit assembly includes a guide catheter,a rotor shroud, and a cannula, with the cannula and guide catheterdisposed on either side of the rotor shroud. The pump assembly includesa rotor, a drive member coupled to the rotor, and a pump disposedbetween the rotor and the drive member. The guide catheter isdimensioned to receive and guide the pump assembly to the point wherethe rotor docks within the rotor shroud so as to form an operationalblood pump. This configuration allows the conduit assembly to beprecisely and efficiently guided into a desired position within the bodythrough the use of conventional guiding techniques well known ininterventional cardiology. The pump assembly may thereafter beintroduced into and guided within the conduit until the pump assembly isdocked within the rotor shroud. This dual construction arrangementprovides improved placement of the pump assembly by using the conduit asa guiding mechanism.

The foregoing broad aspects of the present invention may be manifestedaccording to the following recitations:

According to a first broad recitation of the present invention, anintravascular blood pump system is provided comprising an intravascularblood pump having a cannula coupled thereto, and a guide mechanismadapted to guide the intravascular blood pump and cannula to apredetermined location within the circulatory system of a patient.

In a further embodiment, the intravascular blood pump includes a rotor,a shroud for receiving the rotor, and a drive cable coupled to the rotorfor driving the rotor within the shroud.

In a further embodiment, the cannula is coupled to the shroud of theintravascular blood pump.

In a further embodiment, the guide mechanism comprises a guide cathetercoupled to the shroud.

In a further embodiment, the guide catheter may be used to guide theshroud and cannula to the predetermined location within the circulatorysystem of the patient, after which point the rotor and drive cable ofthe intravascular blood pump may be docked within the shroud for pumpoperation.

In a further embodiment, the drive cable sheath is provided having acentral lumen for receiving the drive cable, and wherein a purge fluiddelivery system is coupled to the drive cable sheath to deliver purgefluid to the rotor.

In a further embodiment, the drive cable sheath includes at least oneside lumen for delivering the purge fluid towards the rotor.

In a further embodiment, a portion of the purge fluid is deliveredthrough the at least one side lumen and past the rotor, and a portion ofpurge fluid is rerouted back from the rotor through the central lumen ofthe drive cable.

In a further embodiment, a perfusion assembly is providedcommunicatively coupled to the guide catheter for selectively reroutingblood from within the guide catheter to a point downstream from theintroduction site of the guide catheter into the vasculature of thepatient.

In a further embodiment, the perfusion assembly includes a first conduitcommunicatively coupled to the guide catheter, a second conduitdimensioned to be introduced into the vasculature of the patient, and aselectively operable valve disposed in between the first conduit and thesecond conduit.

In a further embodiment, a blood pressure detection mechanism isprovided to detect the pressure of the blood proximate at least one ofthe intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanismcomprises at least one of fluid filled column disposed within at least aportion of the cannula, a piezoelectric element coupled to at least oneof the intravascular blood pump and cannula, and a strain gauge coupledto at least one of the intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanism involvescalculating blood pressure based on the relationship between the torqueand motor current of a motor used to drive the rotor.

In a further embodiment, the guide mechanism comprises a guide elementdisposed at least partially within the cannula.

In a further embodiment, the guide element comprises a guide wire forpassage through a side lumen formed in the cannula.

In a further embodiment, the guide element comprises a selectivelydeformable element disposed at least partially within the cannula.

In a further embodiment, the intravascular blood pump and cannula may beselectively advanced to the predetermined location within thevasculature of the patient by first passing the guide wire to thepredetermined location and thereafter sliding the intravascular bloodpump and cannula along the guide wire to the predetermined location.

In a further embodiment, the guide element comprises a guide wire forpassage through a lumen extending through the drive cable and rotor.

In a further embodiment, the intravascular blood-pump and cannula may beselectively advanced to the predetermined location within thevasculature of the patient by first passing the guide wire to thepredetermined location and thereafter sliding the intravascular bloodpump and cannula along the guide wire to the predetermine location.

In a further embodiment, the guide mechanism further includes guideelement for passage through the guide catheter to facilitate placementof the shroud and the cannula at the predetermined location within thevasculature of the patient.

In a further embodiment; the guide mechanism further includes a guideelement for passage through a side lumen formed along at least a portionof the guide catheter.

In a further embodiment, the guide element comprises at least one of aguide wire and a balloon catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a partial sectional view of a human heart illustrating anintravascular blood pump system having an “over-the-wire” type guidemechanism according to a first broad aspect of the present inventionpositioned, by way of example, in a trans-valvular configuration toprovide left-heart assist;

FIG. 2 is side view of the guidable intravascular blood pump system ofthe type shown in FIG. 1 including a motor coupler and purge fluiddelivery system according to an exemplary embodiment of the presentinvention;

FIG. 3 is a cross-sectional view illustrating an exemplary constructionof the blood pump, drive cable assembly, and cannula of theintravascular blood pump system according to the first broad aspect ofthe present invention;

FIG. 4 is a cross-sectional view taken along lines 4-4 of FIG. 3illustrating an exemplary construction of the drive cable assembly andguide mechanism according to the first broad aspect of the presentinvention;

FIG. 5 is a cross-sectional view illustrating an exemplary constructionof the motor coupler and purge fluid delivery system according to thefirst broad aspect of the present invention;

FIG. 6 is a partial sectional view of a human heart illustrating anintravascular blood pump system having a “rapid exchange” or“side-rigger” type guide mechanism according to a second broad aspect ofthe present invention positioned, by way of example, in a trans-valvularconfiguration to provide left-heart assist;

FIG. 7 is side view of the guidable intravascular blood pump system ofthe type shown in FIG. 6 including a motor coupler and purge fluiddelivery system according to an exemplary embodiment of the presentinvention;

FIG. 8 is a cross-sectional view taken along lines 8-8 of FIG. 7illustrating the “side-rigger” or “rapid exchange” type guide mechanismaccording to the second broad aspect of the present invention;

FIG. 9 is a cross-sectional view of the type shown in FIG. 8illustrating an alternate configuration of the guide mechanism accordingto the second broad aspect of the present invention;

FIG. 10 is a partial sectional view of a human heart illustrating anintravascular blood pump system having a “guide catheter” type guidemechanism according to a third broad aspect of the present inventionpositioned, by way of example, in a trans-valvular configuration toprovide left-heart assist;

FIG. 11 is as schematic view of a human being illustrating theintravascular blood pump system of the type shown in FIG. 10 insertedthrough the femoral artery and including an optional perfusion assemblyfor perfusing the vasculature downstream from the incision site whereguide catheter enters the femoral artery;

FIG. 12 is a side view of the intravascular blood pump system shown inFIGS. 10-11 illustrating the separable nature of a pump assembly and aconduit assembly which collectively form the intravascular blood pumpsystem according to the third broad aspect of the present invention;

FIG. 13 is a side view illustrating the intravascular blood pump systemshown in FIG. 12 with the pump assembly docked into the conduit assemblyaccording to the third broad aspect of the present invention;

FIG. 14 is a cross-sectional view illustrating an exemplary constructionof the blood pump, drive cable assembly, cannula, and guide catheter ofthe intravascular blood pump system shown in FIG. 13;

FIG. 15 is a cross-sectional view taken along lines 15-15 of FIG. 14illustrating an exemplary construction of the drive cable assembly andguide catheter according to the third broad aspect of the presentinvention;

FIG. 16 is a cross-sectional view illustrating an exemplary constructionof the motor coupler, purge fluid delivery system, and a proximalportion of the guide catheter biasing assembly according to the thirdbroad aspect of the present invention;

FIG. 17 is a cross-sectional view illustrating an exemplary constructionof the perfusion assembly and a distal portion of the guide catheterbiasing assembly according to the third broad aspect of the presentinvention;

FIG. 18 is a cross-sectional view of an intravascular blood pump systemof the type shown in FIGS. 12-13 having an alternate configuration fordocking the rotor within the shroud according to the principles of thepresent invention; and

FIG. 19 is a partial sectional view of a human heart illustrating analternate intravascular blood pump system having an “over-the-wire” typeguide mechanism according to the first broad aspect of the presentinvention positioned, by way of example, in a trans-valvularconfiguration to provide right-heart assist.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation may bedescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortnight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present invention involves an intravascular pump system for use in anumber of broad ranging applications involving the augmentation of bloodflow within the circulatory system of a patient. As will be describedbelow, the intravascular blood pump system of the present inventionovercomes the drawbacks of the prior art by providing a guide mechanismas part of the intravascular blood pump. This advantageously allows theintravascular blood pump to be selectively guided to a predeterminedlocation within the circulatory system of a patient without the need forbulky supplemental guide mechanisms, such as a separate guide catheter.

The intravascular pump assembly of the present invention is particularlysuited for trans-valvular use, such as for left and/or right ventricularassist procedures. By way of example only, such ventricular assistprocedures may be employed in cardiac operations including, but notlimited to, coronary bypass graft (CABG), cardio-pulmonary bypass (CPB),open chest and closed chest (minimally invasive) surgery,bridge-to-transplant and/or failure-to-wean-from-bypass situations. Itis to be readily understood, however, that the intravascular blood pumpassembly and methods of the present invention are not to be limited tosuch applications. Moreover, while illustrated and described largelywith reference to left-heart assist applications, it is to be readilyunderstood that the principles of the present invention apply equallywith regard to right-heart assist application, which are contemplated aswithin the scope of the present invention. These and other variationsand additional features will be described throughout.

Referring to FIG. 1, shown is a guidable intra-vascular blood pumpsystem 10 according to a first broad aspect of the present inventionshown, by way of example only, in a left-heart assist configurationwithin a human heart. The system 10 includes an intravascular blood pump12, a cannula 14, and an “over-the-wire” type guide mechanism 16. Adrive cable assembly 18 and a motor assembly 20 are provided to drivethe intravascular blood pump 12. The “over-the-wire” guide mechanism 16comprises a suitable guide element dimensioned to pass slideably througha central lumen extending through the drive cable 18, blood pump 12, andcannula 14. Suitable guide elements may include any number ofconventional guiding devices, including but limited to those employed incardiology. By way of example only, the guide element is shown as aguide wire 22. According to the present invention, the “over-the-wire”guide mechanism 16 provides the ability to selectively guide the bloodpump 12 and cannula 14 to a predetermined position in the circulatorysystem of a patient, such as the trans-valvular position shown.

To accomplish this, the guide wire 22 is first introduced into thevascular system of a patient through any suitable access point, such asthrough the use of the well known Seldinger technique. The guide wire 22can then be advanced within the patient to a desired location within thecirculatory system of the patient. This may be done using the controlfeatures of the guide wire 22 itself, or may be facilitated through theuse of any number of supplemental guidance mechanisms or techniques toensure the proper and efficient placement of the guide wire 22. Suchsupplemental guidance techniques may include, but are not necessarilylimited to, guide catheters and/or techniques involving ultra-sound orflouroscopy. Once the guide wire 22 is positioned at the desiredlocation (such as in left ventricle as shown), the blood pump 12 andcannula 14 may thereafter be advanced along the guide wire 22 andpositioned in the trans-valvular configuration shown. Under theoperation of the motor assembly 20, the blood pump 12 may be used forleft-heart assist by selectively withdrawing blood from the leftventricle (through the interior of the cannula 14) for delivery outwardthrough outflow apertures formed in the blood pump 12. This outflow fromthe blood pump 12 flows along the exterior of the drive cable assembly18 in a substantially axial fashion for arterial coupler 24 and, as willbe described in greater detail below, a purge fluid distributionthroughout the body.

Referring to FIGS. 2-5, an exemplary embodiment of the intravascularblood pump system 10 of FIG. 1 will now be described. As shown in FIG.2, the intravascular blood pump system 10 includes a motor deliverysystem 26 for providing a two-way fluid flow within the drive cableassembly 18 during pump operation. The purge fluid delivery system 26includes a fluid inlet conduit 28 for introducing pressurized purgefluid from a fluid source (not shown) for delivery into the blood pump12, and a fluid outlet conduit 30 to withdraw a return flow of purgefluid from the blood pump 12. The motor coupler 24 establishes amechanical connection between a motor (not shown) and a drive cable (notshown) for providing motive force to the blood pump 12 for pumpoperation. The drive cable assembly 18 includes a drive cable sheath 32which, in addition to serving a purge fluid delivery function, alsoserves as a protective housing for the drive cable (not shown). Althoughshown in broken form for clarity, it will be appreciated that the drivecable assembly 18 (and all components thereof) may be provided in anysuitable length sufficient for intravascular applications. That is tosay, the length of the drive cable assembly 18 must be enough to reachbetween the motor coupler 24 and purge fluid delivery system 26, locatedoutside the patient, and the desired location within the patient'scirculatory system where the blood pump 12 is to be positioned.

The intravascular blood pump 12 is shown (by way of example only) as anaxial flow intravascular blood pump. The blood pump 12 includes pumpbody 34, a rotor shroud 36 having flow ports 38, and an internallydisposed rotor (not shown) having a shaft rotatably disposed within thepump body 34 and an impeller rotatably disposed within the rotor shroud36. The cannula 14 is fixedly attached to the rotor shroud 36 and mayextend any suitable length therefrom depending upon the particularintravascular application. The cannula 14 preferably includes aplurality of ports or fenestrations 40 about its distal region, as wellas an end port 42, which allow for the ingress or egress of blood intoor from the cannula 14 depending upon the operation of the blood pump12. That is to say, if the pump 12 is configured for left-heart assistas shown in FIG. 1, then the ports 40, 42 will allow the ingress ofblood into the cannula 14 from the left ventricle. If, on the otherhand, the blood pump 12 is configured for right-heart assist (i.e. withthe pump 12 in the right atrium and the distal end of the cannula 14located within the pulmonary artery), then the ports 40, 42 will allowthe egress of blood from the cannula 14 into the pulmonary artery.(Details on right-heart assist applications will be discussed in greaterdetail below.) The pump 12 and cannula 14 may be dimensioned to anysuitable diameter for intravascular applications. For example, the rangeof sizes may include, but is not necessarily limited to, 9 French to 30French, although the range is more preferably from 14 French to 24French, and most preferably from 18 French to 20 French.

The “over-the-wire” type guide mechanism 16 includes the guide wire 22and, as will be explained in greater detail below, a central lumenextending through the cannula 14, blood pump 12, drive cable assembly18, purge fluid delivery system 26, and motor coupler 24. As notedabove, the central lumen is dimensioned to slideably receive the guidewire 22 such that the blood pump 12 and cannula 14 may be slideablyadvanced along the guide wire 22 to a desired location within thecirculatory system of a patient after the guide wire 22 has been sopositioned using conventional guidance techniques. It is to be readilyunderstood that, while shown as a conventional guide wire 22, the guideelement forming part of the guide mechanism 16 of the present inventionmay include any number of well known guidance mechanisms depending uponthe application, including but not limited to balloon catheters, imagingwires, and guide catheters dimensioned to be slideably received throughthe central lumen. For example, although not appropriate for retrogradeprogression (such as the left-heart application shown in FIG. 1), aballoon catheter may be a suitable guidance mechanism for a right-heartassist application. In such a case, the balloon may be inflated and usedas a “sail” to direct the catheter to a desired location (such as thepulmonary artery), after which point the blood pump 12 and cannula 14can be advanced over the catheter to a trans-valvular configuration withthe blood pump 12 in the right atrium and the ports 38, 40 of thecannula 14 in the pulmonary artery.

FIGS. 3 and 4 further detail the construction of the blood pump 12,cannula 14, drive cable assembly 18, and “over-the-wire” guide mechanism16. The blood pump 12 includes a rotor 44 having a shaft 46 and animpeller 48. The shaft 46 is rotatably disposed within the pump body 34via a bearing pack comprising, by way of example, ball bearingassemblies 50, 52 and spring 54. Ball bearings assemblies 50, 52 arewell known in the art, each comprising an inner race which rotates alongwith the rotor shaft 46, an outer race which remains in a static andfixed position against the inner surface of the pump body 34, and aplurality of ball bearings disposed between the inner and outer races.The spring 54 biases each bearing assembly 50, 52 axially away from oneanother to reduce axial play during pump operation. The shaft 46 isgenerally hollow and dimensioned to receive a cable adapter 60 thereinfor the purpose of coupling the rotor 44 to a drive cable 62 formingpart of the drive cable assembly 18. The drive cable 62 may be securedto the cable adapter 60 in any number of suitable fashions, includingbut not limited to the use of adhesives, crimping, and laser welding.These same techniques may be used to secure the cable adapter 60 withinthe shaft 46 of the rotor 44. A radial seal 64 is provided in betweenthe wall of the pump body 34 and a distal stepped region 66 on the rotorshaft 46, the function of which will be described below.

The impeller 48 includes a hub 56 and a plurality of blades 58 extendingtherefrom. The hub 56 is generally conical and, according to the firstbroad aspect of the present invention, is hollow throughout to form partof the central lumen of the guide mechanism 16. In this regard, the hub56 is preferably provided with a gasket or seal member 68 at its distaltip. The seal member 68 may be made of any suitable sealing material(including but not limited to silicone) such that the pump 12 andcannula 14 may be easily progressed along the guide wire 22 for deliveryto a desired circulatory site. The seal member 68 should also be robustenough to prevent the ingress of blood into the interior of the rotorhub 56 during pump operation, whether the guide wire 22 remains in placeor is fully withdrawn. The blades 58 are dimensioned to reside in closetolerance with the interior surface of the shroud 36. In operation, theblades 58 impart both an axial and radial vector on the blood whichcauses it to flow outward through the flow ports 38 formed in the shroud36. As used herein, the term “axial flow” is deemed to include flowcharacteristics like that shown in FIG. 3, which include both an axialand slight radial component. It is to be readily appreciated that,although shown as an axial flow type, blood pump 12 may comprise anynumber of suitable types of intravascular blood pumps, including but notlimited to so-called “mixed flow” intravascular blood pumps withoutdeparting from the scope of the present invention.

The cannula 14 is coupled at its proximal end to the rotor shroud 36.This may be accomplished in any number of fashions, including but notlimited to the use of adhesives. This may also be facilitated bydimensioning the shroud 36 to include a narrow inlet region 70 capableof being received flushly within the proximal end of the cannula 14. Theinlet region 70 of the shroud 36 should preferably have a taperedinterior surface for establishing a smooth flow transition between thecannula 14 and the region containing the impeller blades 58. Althoughshown as a single integral element, it is to be understood that the pumpbody 34 and shroud 36 may comprise two separate (and sometimesseparable) components, the significance of which will become apparentbelow. The pump body 34 and shroud 36 may be constructed from any numberof suitable materials, including but not limited to stainless steel orother medical grade compositions or alloys. The cannula 14 may also beconstructed from any number of suitable materials, including but notlimited to medical grade plastics. As shown, the cannula 14 may also befortified with spiral-wound reinforcement wire 72 within the walls ofthe cannula 14.

The drive cable assembly 18 includes the drive cable 62 and the drivecable sheath 32. The drive cable 62 is coupled to the rotor 44 via thecable adapter 60. The drive cable sheath 32 includes a central lumen 74and a plurality of side lumens 76. The central lumen 74 serves as aprotective covering for the drive cable 62. The central lumen 74, alongwith the side lumens 76, also forms part of the purge fluid deliverysystem 26 shown above in FIG. 2, which will be described in greaterdetail below. The side lumens 76 are provided in fluid communicationwith the fluid inlet conduit 28, while the central lumen 74 is providedin fluid communication with the fluid outlet conduit 30. The side lumens76 are thus configured to deliver purge, fluid into the pump 12, whilethe central lumen 74 is configured to transport purge fluid away fromthe pump 12 along the length of the drive cable 62.

The pressurized purge fluid within the side lumens 76 may take one oftwo flow paths upon entry into the pump 12. One flow path passes throughthe interior of the pump 12 and onward past the radial seal 64 toprevent the ingress of blood into the pump body 34 during pumpoperation. More specifically, the purge fluid flows distally around thecable adapter 60, through the ball bearing assemblies 50, 52, and onwardpast the radial seal 64. This egress of purge fluid past the radial seal64 can be controlled to effectively thwart the ingress of blood past theradial seal 64, which might otherwise cause clotting and/or pump damage.The other flow path is directed back out the central lumen 74 fordelivery to the fluid outlet conduit 30. In so doing, this flow pathbathes the components of the pump 12 and/or drive cable 62 and therebyreduces frictional heating within the pump 12 and/or the central lumen74 of the sheath 32 during pump operation.

The “over-the-wire” guide mechanism 16 includes a central lumen throughwhich the guide wire 22 may extend for the purpose of slideablyadvancing the blood pump 12 and cannula 14 into a desired positionwithin the circulatory system of a patient. In the embodiment shown,this central lumen is established by forming and co-aligning theindividual central lumens within each of the drive cable 62, the cableadapter 60, the shaft 46 and hub 56 of the rotor 44, and the cannula 14.In this regard, the drive cable 62 is preferably of wound-wireconstruction having a central lumen formed therein. The central lumenswithin the cable adapter 60, rotor 44, and gasket 68 may be formed viamachining or molding processes. These central lumens should preferablybe sized such that they permit the slideable passage of the pump 12 andcannula 14 therealong, but do not interfere with or constrain the guidewire 22 to cause inadvertent rotation of the guide wire 22 during pumpoperation. As noted above, it is also contemplated to remove the guidewire 22 after the pump 12 and cannula 14 are properly positioned in thepatient. In this case, the gasket or seal 68 on the hub 56 should berobust enough to reseal after the guide wire 22 is withdrawn and preventthe ingress of blood into the interior of the rotor 44.

Referring to FIG. 5, the motor coupler 24 includes a housing 78, a driveshaft adapter 80, and a bearing assembly 82. The drive shaft adapter 80includes a drive shaft coupler 84 dimensioned to receive a drive shaftof a motor (not shown), and a drive cable coupler 86 dimensioned toreceive the drive cable 62. Any of a variety of attachment techniquesmay be employed to securely fasten the drive cable 62 to the drive cablecoupler 86, including but not limited to adhesives, crimping, and laserwelding. The drive shaft adapter 80 is rotatably disposed within thehousing 78 by the bearing assembly 82. The bearing assembly 82 includesa sleeve 88 (which may alternatively be formed as an integral part ofthe housing 78) for retaining a pair of ball bearing assemblies 90, 92and a spring 94 of the type described above. That is, each bearingassembly 90, 92 generally comprises an inner race which rotates alongwith the drive shaft adapter 80, an outer race which remains in a staticand fixed position against the inner surface of the retaining sleeve 88,and a plurality of ball bearings disposed between the inner and outerraces. The spring 94 is provided to bias each bearing assembly 90, 92axially away from one another to reduce axial play during operation.

The purge fluid delivery system 26 includes a housing 96 having acentral lumen 98, an inflow port 100, and an outflow port 102. Thehousing 96 is also dimensioned to matingly receive a portion of themotor coupler 24. In this regard, a seal element 104 is providedsandwiched in between the housing 96 and housing 78 and including anaperture which extends about the drive shaft adapter 80 as it exits thehousing 78 to prevent the ingress of purge fluid into the motor coupler24. A fluid guide structure 106 is also provided within the centrallumen 98 for the purpose of separating the inflow and outflow ports 100,102. The fluid guide structure 106 includes a central lumen 108 throughwhich the drive cable 62 extends, and an elevated portion 110 thatretains an O-ring 112 against the inner surface of the central lumen 98of the housing 96. The drive cable sheath 32 is secured to the housing96 such that the inflow port 100 is communicatively coupled to the sidelumens 76, and the outflow port 102 is communicatively coupled to thecentral lumen 74. In this fashion, pressurized purge fluid may beintroduced through the inflow port 100 via inflow conduit 28, andremoved through the outflow port 102 via outflow conduit 30. By way ofexample, the inflow conduit 28 and outflow conduit 30 may be coupled totheir respective ports 100, 102 via barbed connectors 114. Similarly,the inflow and outflow conduits 28, 30 may be equipped with any numberof suitable connectors (such as those illustrated by way of example inFIG. 2) for establishing fluid communication with a source ofpressurized fluid (not shown). The pressurized fluid source (not shown)may include, but is not necessarily limited to, the use of a syringe, anindeflator, a fluid delivery pump, or an accumulator arrangement toprovide the requisite delivery of pressurized fluid. The purge fluiddelivery system 26 thus provides a two-way transmission of purge fluidwithin the drive cable sheath 32 for the purposes of cooling the bloodpump 12 and preventing the ingress of blood past the radial seal 64 andinto blood pump 12.

Referring to FIG. 6, shown is a guidable intra-vascular blood pumpsystem 120 according to a second broad aspect of the present invention.As will be described hereinafter, the intravascular blood pump system120 differs from the intravascular blood pump system 10 described aboveonly as to the type of guide mechanism employed. In the interest ofclarity and consistency, then, like reference numerals will be used todenote like elements and distinctions pointed out where necessary.Moreover, due to the commonality of principles employed in bothintravascular blood pump systems 10, 120, a discussion to the level ofdetail set forth above is not deemed necessary with regard to theintravascular blood pump system 120. Instead, those aspects in commonwith the intravascular blood pump 10 are hereby incorporated into thediscussion of the intravascular blood pump system 120.

In its most general form, the intravascular blood pump system 120 ofthis second broad aspect of the present invention comprises the bloodpump 12 and cannula 14 arrangement, wherein the cannula 14 is equippedwith a “side-rigger” or “rapid exchange” guide mechanism 122. In animportant aspect of the present invention, the “rapid exchange” or“side-rigger” guide mechanism 122 includes a guide carriage 124 formedalong at least a portion of the cannula 14, and a suitable guide element(such as guide wire 22) dimensioned to pass slidably through a lumen(not shown) extending through the guide carriage 124. The “rapidexchange” guide mechanism 122 thereby provides the ability toselectively guide the blood pump 12 and cannula 14 to a predeterminedposition in the circulatory system of a patient in the manner describedabove. Namely, the guide wire 22 may be first introduced into thevascular system of a patient through any suitable access point andguided to a desired location within the circulatory system of thepatient, i.e. the left ventricle as shown. The blood pump 12 and cannula14 may thereafter be advanced along the guide wire 22 and positioned inthe trans-valvular configuration shown for providing left-heart assist.

FIGS. 7-9 further illustrate the “side-rigger” or “rapid-exchange” guidemechanism 122 of this second broad aspect of the present invention. In apreferred embodiment, the “side-rigger” guide mechanism 122 includes alumen 126 formed within the guide carriage 124. The guide carriage 124is preferably formed as an integral extension of the wall of the cannula14. FIGS. 7 and 8 comport with the embodiment shown in FIG. 6, namelyillustrating the guide carriage 124 formed along the exterior surface ofthe cannula 14. FIG. 9 illustrates an alternate embodiment wherein theguide carriage 124 may be formed along the interior surface of thecannula 14. In either case, the guide wire 22 is advanced to a desiredlocation in the vasculature of the patient, after which point the bloodpump 12 and cannula 14 can be slidably advanced therealong for deliveryto the desired location according to the present invention. The guidewire 22 may thereafter be withdrawn from the patient. If the guidecarriage 124 is formed along the exterior surface of the cannula 14 (asshown in FIGS. 7-8), then the cannula 14 should preferably be positionedso that the guide carriage 124 does not extend in a trans-valvularfashion. For example, with reference to FIG. 6, the guide carriage 124should be positioned wholly within the left ventricle such that thepulsatile blood flow during beating heart procedures will notinadvertently pass through the side lumen 126 and pass through theaortic valve.

The intravascular blood pump system 120 is constructed in virtually thesame manner as the intravascular blood pump system 10 shown anddescribed above, with the exception of the location of the respectiveguide mechanisms 16, 122. More specifically, because the guide mechanism122 is disposed along the side of the cannula 14, there is no need toform a central lumen extending through the blood pump 12, drive cableassembly 18, purge fluid delivery system 26, and motor coupler 24 asdetailed above with regard to the intravascular blood pump system 10. Assuch, these components need not be specially machined or molded toinclude such central lumens as was required with the intravascular bloodpump system 10 set forth above.

Referring to FIG. 10, shown is a guidable intravascular blood pumpsystem 130 according to a third broad aspect of the present invention.Again, due to the commonality between many of the same components andfeatures of the intravascular blood pump systems described above and theintravascular blood pump system 130, like reference numerals will beused to denote like elements and distinctions pointed out wherenecessary. As will be explained in greater detail below, theintravascular blood pump system 130 employs yet another unique anduseful guide mechanism according to the present invention. However,because many of the same components are employed, a discussion to thelevel of detail set forth above is not deemed necessary with regard tothe intravascular blood pump system 130. Instead, those aspects incommon with the intravascular blood pumps described above are herebyincorporated into the discussion of the intravascular blood pump system130.

In its most general form, the intravascular blood pump system 130 ofthis third broad aspect of the present invention comprises the bloodpump 12 and cannula 14 arrangement, wherein a “guide catheter” 132 isprovided as the guide mechanism for positioning the pump 12 and cannula14 at a desired location within the circulatory system of the patient.More specifically, with brief reference to FIG. 12, the intravascularblood pump system 130 is formed in two separate assemblies according tothe present invention: a conduit assembly 134 and pump assembly 136. Inits most basic form, the conduit assembly 134 comprises the guidecatheter 132 and cannula 14 coupled to the. Rotor shroud 35. The pumpassembly 136 is constructed such that the pump body 34 and rotor 44 canbe disengaged from the rotor shroud 36 and removed entirely from theconduit assembly 134. Referring again to FIG. 10, this dual constructionforms a significant feature of the present invention because it providesthe ability to form the blood pump 12 at a desired location in a patientusing two separate and distinct steps. The first step involvespositioning the conduit assembly 134 (with the pump assembly 136removed) within a patient such that the shroud 36 and cannula 14 areeach disposed in a desired location, such as a trans-valvularconfiguration for cardiac assist procedures. In an important aspect, thetask of positioning the conduit assembly 134 within the patient may beadvantageously facilitated through the use of any number of well knownguidance mechanisms, including but not limited to guide wires, ballooncatheters, imaging wires, guide catheters, and/or techniques involvingultra-sound or flouroscopy. The second step in providing theintravascular blood pump system 130 of the present invention involvesadvancing the pump assembly 136 through the conduit assembly 134 suchthat the rotor 44 docks within the shroud 36 to form the pump 12 at thedesired location.

By way of clarification, the term “cannula” is used to denote cannula 14because it serves a primary purpose of transporting fluid into the bloodpump 12, whereas the term “catheter” is used to denote the catheter 132because it serves a primary purpose of guiding or directing devices orcomponents (i.e. the pump assembly 136) to a desired location within thebody. It is to be readily understood, however, that these terms are onlyused for convenience and in a general fashion such that the cannula 14may serve certain guiding functions and the catheter 132 may servecertain fluid transportation functions without departing from the scopeof the present invention. For example, the cannula 14 may be equippedwith dedicated lumens to receive various guide mechanisms (such as guidewires, balloon catheters, selectively deformable elements such asNitonol, etc). In similar fashion, the guide catheter 132 may be used totransport fluid to and/or from the patient, such as by providingapertures 138 along predetermined regions of the catheter 132.

FIG. 11 demonstrates a significant feature of the present inventioninvolving the use of the guide catheter 132 to transport fluid to and/orfrom the patient. An optional perfusion assembly 140 is provided as partof the intravascular blood pump system 130 of the present invention. Theperfusion assembly 140 includes a conduit 142 in fluid communicationwith the apertures 138, which in this case are formed near the distalregion of the guide catheter 132 a short distance downstream from theblood pump 12. In use, blood will pass along the exterior of the guidecatheter 132 for distribution throughout the body, as well as within theinterior of the guide catheter 132 after passing into the apertures 138.The perfusion assembly 140 may then be employed to selectively rerouteblood from within the guide catheter 132 to a point within the patient'svasculature downstream from the point where the guide catheter 132enters the body. A hemostasis valve assembly 146 of the perfusionassembly 140 permits the drive cable assembly 18 to pass through to thepurge fluid delivery system 26 while preventing blood flow other thaninto the perfusion assembly 140. A seal assembly 150 of the purge fluiddelivery system 26 permits the drive cable 62 to pass through to themotor 20 while preventing the flow of purge fluid other than into andfrom the purge fluid delivery system 26. The perfusion assembly 140includes a control mechanism 148 for selectively controlling thedistribution of perfusion blood flow from the perfusion assembly 140into the patient. This control mechanism 148 may be automatic based oncertain feedback criteria or manually operated.

FIGS. 12-17 illustrate an exemplary construction of the intravascularblood pump system 130 according to the third broad aspect of the presentinvention. As shown in FIG. 12, the conduit assembly 134 may beselectively disengaged so as to remove the pump assembly 136 therefrom.According to the present invention, the conduit assembly 134 may beintroduced (without the pump assembly 136) into the circulatory systemof a patient and selectively guided such that the rotor shroud 36 andcannula 14 are positioned at a desired location. The pump assembly 136can thereafter be selectively introduced into the conduit assembly 134.A challenge in such a “back-loading” arrangement is ensuring that thepump assembly 136 docks appropriately within the rotor shroud 36 and ismaintained in proper engagement during operation of the resulting pump12.

An exemplary docking arrangement will now be described with reference toFIG. 14. In a preferred embodiment, the rotor 44 may be properly andaccurately docked within the shroud 36 by forming angled mating surfaceson corresponding portions of the shroud 36 and pump body 34. Morespecifically, an angled mating surface may be formed on the interiorsurface of the rotor shroud 36 along that portion extending proximallyfrom the flow aperture 38. A corresponding angled mating surface may beprovided along the exterior surface of the pump body 34 along a distalportion thereof. The mating surfaces shown in FIG. 14 may preferably beformed in the range from about 2 degrees to 10 degrees, and morepreferably formed in the range from about 3 degrees to 6 degrees. Matingangles within these ranges are adequate to guide the distal end of thepump body 34 to a point generally flush with the proximal edge of theflow aperture 38 as shown in FIG. 14. In this fashion, the pump assembly136 and the rotor shroud 36 combine to form the blood pump 12. Moreimportantly, this docking is carried out such that the rotor 44 androtor blades 58 are maintained in proper position for efficient and safepump operation.

An exemplary biasing scheme for maintaining the pump assembly 136 inthis docked relationship will now be described with reference to FIGS.12-13 and 16-17. The conduit assembly 134 is preferably equipped with amale quick-connect coupling 152 capable of engaging with a femalequick-connect coupling 154 forming part of the perfusion assembly 140 ofthe present invention. A bias spring 156 is provided in between theperfusion assembly 140 and the housing 96 of the purge fluid deliverysystem 26. The bias spring 156 is preferably dimensioned so as to be intension when the male quick-connect 152 is engaged within the femalequick-connect 154 as part of the docking process of the presentinvention. As such, the bias spring 156 serves to maintain the pumpassembly 136 in the docked position within the rotor shroud 36. The biasspring 156 may be coupled to the housing 96 of the purge fluid deliverysystem 26 in any number of suitable fashions. One such couplingarrangement may comprise a female quick-connect coupling 158 attached tothe housing 96 and a male quick-connect coupling 160 attached to thebias spring 156.

An exemplary embodiment of the perfusion assembly 140 is shown withreference to FIGS. 12-13 and 17. The perfusion assembly 140 shownincludes the hemostasis valve 146 coupled to the female quick-connectcoupling 154. A length of tubing 162 extends between the opposing barbconnectors of the hemostasis valve 146 and the female quick-connectcoupling 154. A continuous lumen is formed extending through theinterior of the male quick-connect coupling 152, thefemale-quick-connect coupling 154, the tubing 162, and the hemostasisvalve 146. The drive cable assembly 18 extends through this continuouslumen and exits through a Touehy-Borst hemostasis seal 164 whichprevents the migration of blood out of the proximal end of the perfusionassembly 140. A side-port 166 is disposed in fluid communication withthe central lumen of the perfusion assembly 140. In one embodiment, thisside-port 166 may be equipped with a conduit 168 having a stop-cock 170to selectively control the distribution of blood through a perfusionconduit (i.e. conduit 142 of FIG. 11) coupled to the stop-cock 170. Itwill be appreciated that this type of manual control system forselectively perfusing the patient may be replaced with control circuitryfor automatically controlling the rate of perfusion. Such automaticperfusion may be based on control algorithms based on contemporaneousfeedback or pre-programmed thresholds.

The foregoing discussion details a host of inventive aspects formingpart of the present invention. It will be appreciated by those skilledin the art that changes could be made to the embodiments described abovewithout departing from the broad inventive concepts thereof. Thefollowing evidences, by way of example only, various additional aspectsforming part of the present invention.

FIG. 18 illustrates an alternate configuration of the intravascularblood pump system 130 of the third broad aspect of the present inventionhaving an alternate bearing assembly, purge fluid delivery, and dockingscheme. The bearing assembly includes a seal spring 182 and a bearingassembly 180. The bearing assembly 180 includes an inner race 184, anouter race 186, and a plurality of balls 188 which enable the inner race184 to rotate along with the rotor shaft 46 while the outer race 186remains in a static and fixed position relative to an inner surface ofthe pump body 34. An O-ring 190 is disposed within a groove formed inthe rotor shaft 46 so as to maintain the bearing assembly 180 againstthe seal spring 182. The O-ring 190 is further secured within the groovein the rotor shaft 46 via a contoured lip portion extending from thedistal end of the cable adapter 60. The proximal end of the cableadapter 60 flushly engages the drive cable 62.

The purge fluid delivery system of the embodiment shown in FIG. 18provides for a one way delivery of purge fluid to the blood pump 12.That is, pressurized fluid (namely, fluid pressurized to some levelelevated above the blood pressure in the surrounding vessel) is injectedin between the drive cable 62 and the interior of the protective sheath32 during operation. This serves to reduce any frictional heating thatexists between the drive cable 62 and sheath 32. The pressurized fluidalso flows through the interior of the pump 12 such that, if the seal at192 is broken, the pressurized fluid will flow past the open seal 192and onward through the blood flow ports 38 formed in the shroud 36. Thisserves to keep blood from entering the pump 12 in an effort to avoidclotting and/or damaging the pump 12.

The pump assembly 136 may be docked within the conduit assembly 134 inany number of different fashions without departing from the scope of thepresent invention. That is to say, the docking scheme shown in FIG. 18is set forth by way of example only and is not to be deemed limiting orrestrictive as to numerous ways to temporarily engage or “dock” the pumpassembly 136 within the conduit assembly 134. The only requirement isthat the pump assembly 136 and conduit assembly 134 dock such that therotor 44 is disposed within the shroud 36 to provide the desired axialflow through the cannula 14 and out the shroud 36. The exemplary dockingscheme involves forming an annular engagement groove 194 along theinterior of the shroud 36, and forming a complementary annular ridge 196along the exterior surface of the pump body 34. During insertion, thepump assembly 136 will be advanced into the conduit assembly 134 untilthe annular ridge 196 on the pump body 34 engages within the groove 194formed in the shroud 36. This docking scheme is generally advantageousin that the engagement action between the annular ridge 196 and groove194 will provide tactile feedback to the physician during the process ofinserting the pump assembly 136 into the conduit assembly 134 such thatthe physician will be able to determine when the docking has beencompleted.

As will be appreciated by those skilled in the art, the location of theannular ridge 196 and engagement groove 194 may be varied such that theyare disposed closer or farther away from the flow apertures 38. It maybe advantageous to form these docking structures close to the flowapertures 38 in an effort to thwart the ingress of blood into thejunction extending between the interior of the shroud 36 and theexterior surface of the pump body 34. It is also contemplated to employselectively inflatable structures, such as balloons, in an effort totemporarily engage or dock the pump assembly 136 within the conduitassembly 134. In this regard, one or more lumens may be formed withinthe pump body 34 extending from the interior of the pump body 34 influid communication with a balloon disposed along the exterior surfaceof the pump body 34. The pressurized fluid flowing within the interiorof the pump body 34 may then be used to inflate the balloon, which willthen engage within an annular groove in the shroud 36, such as at 194.Of course, the engagement structures may also be reversed withoutdeparting from the scope of the present invention. For example, theshroud 36 may be equipped with a fluid delivery lumen therein forinflating a balloon disposed on the interior surface of the shroud 36,which may in turn be disposed within an annular engagement groove formedalong the exterior surface of the pump body 34.

While this invention has been shown in use largely in during left-heartapplications it is to be readily appreciated that this does not limitthe applications of this invention for use in left heart support only.Rather, the guidable intravascular blood pump of the present inventioncan be utilized in right-heart support applications and a wide varietyof other applications apparent to those skilled in the art. For example,with reference to FIG. 19, shown is an intravascular blood pump 200 (ofthe type shown and described above with reference to FIGS. 2-5)configured for use in a right-heart support application. In thisembodiment, the intravascular blood pump system 200 is equipped, by wayof example, with an “over-the-wire” guide mechanism 16 comprising aballoon catheter 202. It is to be readily appreciated that, althoughshown and described below in terms of an embodiment of the type shown inFIGS. 2-5, the intravascular blood pump systems 120, 130 disclosedherein may also be configured for use in right-heart applications. Suchright-heart configurations, and others apparent to those skilled in theart based on the broad principles enumerated in this application, arecontemplated as being within the scope of the present invention.

The intravascular blood pump system 200 is shown positioned within theheart, such as may be advantageous to provide right heart support duringbeating heart surgery. To position the guidable intravascular blood pumpsystem 200 in the right heart according to the present invention, asuitable guide element (such as balloon catheter 202) is first advancedto a desired location within the heart via the “sail” action of aninflated balloon. After the balloon catheter 202 is located in thedesired position (such as in the pulmonary artery as shown), theintravascular blood pump system 200 according to the present inventionmay be advanced over the balloon catheter 202 and guided into a desiredarrangement. For right heart support, this would involve advanced intothe pump 12 and cannula 14 overt the balloon catheter 202 until thefluid inlet 204 is disposed within the vena cava (or right atrium) andthe fluid outlet 206 is positioned within the pulmonary artery. The pump12 may then be selectively (i.e. automatically or on-demand) controlledto transport blood from the vena cava (or right atrium) in atrans-valvular fashion through the tricuspid valve, the right ventricle,and the pulmonary valve for deposit within the pulmonary artery.Providing right-heart support during beating heart surgeryadvantageously overcomes conditions where cardiac output may becomecompromised during beating heart surgery, such as when the heart islifted to gain access to posterior vessels, thereby avoiding the needfor cardiopulmonary bypass.

It is also contemplated as part of the present invention that theguidable intravascular blood pump systems can be introduced into thepatient's vasculature to achieve the intravascular access into the rightor left heart through any number of access points, including but notlimited to the internal jugular vein, the brachiocephalic vein, carotidartery, axillary artery, femoral vein, femoral artery, and subclavianartery. The intravascular blood pump systems of the present inventionmay also be introduced via direct introduction, such as into the aorta,the atria, and the ventricles. As is well known in the art, suchintravascular access may be achieved percutaneously through the use ofthe Seldinger technique or directly through the use of minimallyinvasive access techniques.

Those skilled in the art will also appreciate that, although shown anddescribed above in terms of “axial flow,” the present invention is notlimited to the axial flow type intravascular blood pumps. Rather, theintravascular blood pumps 12 may comprise any number of suitable typesof intravascular blood pumps, including but not limited to so-called“mixed flow” intravascular blood pumps, without departing from the scopeof the present invention.

With regard to the embodiments shown in FIGS. 10-17, it is furthermorecontemplated that the guide catheter 132 may be separable from theconduit assembly 134 after the pump assembly 136 is docked within theshroud 36 to form the pump 12 at the desired location within thecirculatory system of the patient. This may be accomplished by providingthe guide catheter 132 in a detachable fashion via any number ofsuitable arrangements. By removing the guide catheter 132 after the pump12 assembled, wound management of the access point into the patient'svasculature may be improved. This is due, in part, to the substantialreduction in size of the device extending into the patient (i.e. thedrive cable assembly 18 as opposed to the larger diameter guide catheter132).

It is also contemplated to incorporate various pressure sensing and/orguidability features into at least one of the cannula, 14 and pump 12.Such features may include, but are not necessarily limited to, thoseshown and described in commonly-owned and co-pending U.S. patentapplication Ser. No. 09/280,988 (filed Mar. 30, 1999) entitled“Steerable Cannula,” and U.S. patent application Ser. No. 09/280,970(filed Mar. 30, 1999) entitled “Pressure Sensing Cannula,” thedisclosures of which are hereby expressly incorporated by reference asif set forth herein in their entirety. These pressure sensing featuresmay include, but are not necessarily limited to, the use of fluid-filledlumens, piezo-electric pressure sensing elements, strain gauges, andanalysis of the torque/current relationship (based on the dynamicpressure differential between the inlet and outlet of the pump). Theguidability features may include, but are not necessarily limited to,the use of side lumens and deformable materials (i.e. Nitonol).

Various pump and cannula arrangements have been described and shownabove for providing right and/or left heart support wherein blood isdeliberately re-routed through and past the right and/or left ventriclein an effort to reduce the volume of blood to be pumped by theparticular ventricle. While “unloading” the ventricles in this fashionis preferred in certain instances, it is to be readily understood thatthe pump and cannula arrangements described herein may also be employedto “preload” the ventricles. Ventricular preloading may be accomplishedby positioning the outflow cannula from the pump into a given ventriclesuch that the pump may be employed to fill or preload the ventricle withblood. This may be particularly useful with the right ventricle. Onoccasion, the right ventricle is not supplied with sufficient levels ofblood from the right atrium such that, upon contraction, the rightventricle delivers an insufficient quantity of blood to the pulmonaryartery. This may result when the right ventricle and/or right atrium arein a stressed or distorted condition during surgery. Preloadingovercomes this problem by actively supplying blood into the rightventricle, thereby facilitating the delivery of blood into the pulmonaryartery. The same technique can be used to preload the left ventricle andthus facilitate the delivery of blood from the left ventricle into theaorta.

What is claimed is:
 1. A method for perfusing a patient with anintravascular blood pump system, the intravascular blood pump systemcomprising (i) an intravascular blood pump comprising a rotor having arotor hub tapering in the distal direction, at least one blade extendingradially outward from the rotor hub, the hub having a distal endextending distally beyond the most distal portion of the blade and ashroud within which the rotor is rotatably disposed; (ii) a cannulaextending from the shroud and comprising an outer cannula surface, theouter cannula surface having a substantially circular cross-sectionalong a portion of its length; (iii) a first lumen in fluidcommunication with the intravascular blood pump and operatively arrangedto deliver purge fluid to the intravascular blood pump; and (iv) a guidemechanism configured as a second lumen having a proximal end and adistal end, the guide mechanism adapted to guide a distal portion ofsaid intravascular blood pump system to a predetermined location withinthe circulatory system of a patient, wherein an axis coaxial with andextending through a portion of said guide mechanism extends through aregion delimited by the outer cannula surface, and wherein the guidemechanism is configured to allow for a guide wire to slideably advancetherealong, the method comprising the steps of: progressing a guide wireto a predetermined location in the circulatory system of the patient;and advancing the blood pump system along the guide wire to thepredetermined location.
 2. The method of claim 1, wherein the rotorcomprises a second blade extending radially from the rotor hub and therotor hub is generally conical.
 3. The method of claim 1, wherein adistal end of the cannula is open in order to enable the guide wire topass axially through the distal end of the cannula.
 4. The method ofclaim 1, wherein the guide mechanism is configured such that the guidewire passes through the region delimited by the outer cannula surface ata location proximal to where the guide wire establishes slidable contactwith the guide mechanism.
 5. The method of claim 1, wherein the secondlumen has an inner diameter along a portion of its length that issubstantially smaller than an outer diameter of the outer cannulasurface, and the lengh of the second lumen is substantially longer thanthe inner diameter of the second lumen.
 6. The method of claim 1,further comprising a guide catheter, wherein the guide catheter isconfigured to facilitate the placement of the guide wire into the heart.7. The method of claim 1, further comprising: an elongate catheterextending proximally with respect to the intravascular blood pump; and ablood pressure detection mechanism comprising a fluid column disposedwithin the catheter and configured to detect the pressure of the bloodproximate the intravascular blood pump.
 8. The method of claim 1,wherein the cannula is operatively arranged to bend at a locationbetween distal and proximal ends thereof.
 9. The method of claim 1,further comprising a first conduit and a second conduit, at least one ofthe first conduit or the second conduit terminating in a fitting that isconfigured to be located outside a patient when the intravascular bloodpump and cannula are located inside the patient, at least one of thefirst conduit and second conduit in fluid communication with the firstlumen.
 10. A method for perfusion a patent with an intravascular bloodpump system, the intravascular blood pump system comprising (i) anintravascular blood pump comprising a rotor having a rotor hub taperingin the distal direction and at least one blade extending radiallyoutward from the rotor hub, the intravascular blood pump coupled to acatheter on a proximal end and a cannula on a distal end; (ii) a firstset and a second set of apertures establishing fluid communicationbetween an interior of the cannula and an exterior region of thecannula, wherein the first set of apertures is located in proximity tothe rotor and the second set of apertures is spaced apart from andlocated distal to the first set of apertures towards a distal region ofthe cannula; (iii) a guide mechanism configured as an elongate lumen andadapted to guide said intravascular blood pump, cannula, and catheter toa predetermined location within the circulatory system of a patient; and(iv) a blood pressure detection mechanism comprising a fluid columnconfigured to detect the pressure of the blood proximate theintravascular blood pump; wherein the elongate lumen (a) is sizedsubstantially smaller than an inner diameter of the cannula andintravascular blood pump; (b) is arranged coaxially with at least one ofa distal end or a proximal end of the cannula, and (c) is arranged inseries longitudinally with the cannula: the method comprising: advancinga guide wire to a predetermined location in the circulatory system ofthe patient; and advancing the blood pump system along the guide wire tothe predetermined location.
 11. The method of claim 10, furthercomprising a guide wire and a guide catheter, wherein the guide catheteris configured to facilitate the placement of the guide wire through thevasculature into the heart.
 12. The method of claim 10, wherein thecannula comprises an outer cannula surface having a substantiallycircular cross-section along a portion of its length, and the cannula isreinforced with a spiral wire.
 13. The method of claim 10, furthercomprising a plurality of egress flow ports disposed in a shroud of theintravascular blood pump, and a plurality of ingress flow ports disposedat a location spaced apart from and distal to the egress flow ports. 14.The method of claim 13, wherein the ingress flow ports comprise an endport located at the cannula distal end and a plurality of ports locatedabout the cannula and proximal to the end port.
 15. The method of claim10, wherein the first set of apertures are egress ports and the secondset of apertures are ingress ports, and wherein the egress ports areconfigured to direct blood passing through the interior of the cannulaand towards the rotor in a direction that is both proximal and radiallyoutward with respect to the rotor hub.
 16. The method of claim 10,wherein the elongate lumen extends centrally through the cannula andblood pump.
 17. The method of claim 10, wherein the elongate lumen isproximal to the cannula.
 18. The method of claim 10, wherein the cannulais operatively arranged to bend at a location between distal andproximal ends thereof.
 19. The method of claim 10, wherein the distalend of the cannula is open to enable the guide wire to pass axiallythrough the distal end of the cannula.
 20. A method for perfusion apatent with an intravascular blood pump system, the intravascular bloodpump system is configured to be advanced to a predetermined location ina patient's circulatory system and comprises (i) an intravascular bloodpump, the intravascular blood pump comprising a rotor having a generallyconical rotor hub tapering in the distal direction, at least two bladesextending radially from the rotor hub, the generally conical rotor hubhaving a distal tip extending distally beyond the blades; (ii) a cannulaextending distally from the intravascular blood pump; (iii) a pluralityof ingress ports located towards the distal region of the cannula and aplurality of egress ports located in proximity to the blood pump suchthat movement of fluid proximally through an interior region of thecannula is steered towards the egress ports; (iv) a guide wire having across-section substantially smaller than the cannula; and (v) anelongate lumen, the elongate lumen (a) having a luminal interior sizedsmaller than an inside diameter of the cannula and sufficiently largeenough to accommodate the guide wire when the guide wire is advancedtherealong, (b) arranged coaxially with respect to at least one of adistal end or a proximal end of the cannula, and (c) arranged in serieslongitudinally with the cannula, the method comprising: advancing theguide wire to a predetermined location in the circulatory system of thepatient; and advancing the blood pump along the guide wire to thepredetermined location.
 21. The method of claim 20, wherein the lumen isproximal with respect to the cannula.
 22. The method of claim 20,wherein the distal end of the cannula is open to enable the guide wireto pass axially through the distal end of the cannula.